Looms without shuttle have gained more and more ground in the textile field, supplanting, except specific cases, the conventional shuttle looms. Today they account for about 70% of the existing looms and will more and more cover the remaining 30% of the old shuttle looms as the latter will go out of service.
The shuttleless loom, though having an enormously higher productivity, however presents a drawback versus the shuttle loom, since it has to draw the weft yarn from a reel that has diameters varying from 20-25 cm (full reel) to 4-6 cm (empty reel). This involves high differences of unwinding tension (very low with full reel, very high with empty reel). The shuttle loom, taking the weft from a spool (average diameter 2-4 cm) is not affected by these differences. The great productive superiority of the shuttleless loom has aroused the need of finding a device that, when positioned between reel and loom, could cancel the difference of yarn tension between full reel and empty reel, allowing the yarn take-up member of the shuttleless loom to loom insert the weft at a constant tension.
A device is known essentially consisting of a rotary drum with cone ramp at one end and a ring with very fine nickings, angled with respect to the drum axis, at the other end. The drum, while rotating under the control of a motor, takes the yarn from the reel, winds it on itself from the cone section, and thanks to the latter, arranges the yarn in parallel and not superimposed ranks on its cylindrical section. Said yarn then comes out from the front end of the drum, held by a very light ring on which rather stiff nylon threads are inserted to act like a brush (said stiffness varies according to the treated yarn and the insertion speed). The nylon threads, engaging the above described nickings, prevent the ring and the yarn from having a relative movement with respect to the direction of rotation of the drum.
The yarn, stressed in traction by the take-up member of the loom, with a minimal effort lifts the brush hair and inserts itself as weft in the loom. Simultaneously the brush ring prevents the relative movement of the yarn on the drum with consequent entanglement. The length of the yarn reserve on the drum is controlled by a photoelectric cell which acts on the rotation of the drum. In recent years however the speeds of the weft insertion on the shuttleless looms were more and more increased. The first looms inserted, on a length of 3.30 mt, 180-200 wefts per minute corresponding to about 800-880 meters per minute, and this for single-colored looms. If the loom, as in most cases, worked with 2 or 4 colors or with weft mixing, the average speed required to the weft supplier device was to 4 times lower (also according to the nature of the fabric drawing).
Later these parameters changed, and looms 4 and even 5 meters wide were used with 220 to 250 insertions per minute and at the present time even higher. Therefore the speed required today to a weft supplier ranges from a minimum of 880 to 1200 meters per minute and even more. Under these conditions the weft suppliers of first generation were no longer capable to supply such looms in that, at speeds exceeding 500-600 meters per minute, the brush hair on top of the drum rise due to the centrifugal force, no longer assuring the absence of relative movement of the yarn with respect to the drum, thus causing the yarn entanglement.